Child–matter relations are often approached teleologically: as serving a distinct purpose often related to socialization and/or development as maturation. Unless these approaches are diversified, children’s relations to their material surroundings are reduced to instrumental activity the significance of which is predetermined and known by adults. This article is based on a study with 12 Finnish children of ages four to seven, exemplifying a new materialist and post-humanist approach to child–matter relations as intra-active. Children’s engagement with ‘things’ is considered intrinsically relevant: as an end in itself. The questions asked are: How do children and their material surroundings intra-act? What is produced in this intra-action? Two characteristics of child–matter intra-action are identified as mingling and imitating. What the intra-action is seen to produce are spaces of open-ended and de-individualized knowing and being.